Apparatus comprising a fuel cell unit and a component, a stack component for use in such an apparatus

ABSTRACT

A fuel cell unit with a plurality of fuel cells defining a longitudinal axis and a main flow direction coaxial to the longitudinal axis. Fuel cell inlets and fuel cell outlets are arranged at opposite ends of the fuel cell unit and in line with the main flow direction. Also, a component comprising first fluid conduits arranged parallel to the main flow direction, the first fluid conduits comprising first fluid inlets and first fluid outlets arranged at opposite ends of the component and in line with the main flow direction. The component is arranged adjacent the fuel cell unit such that at least one of the first fluid inlets and the first fluid outlets of the component are arranged adjacent at least one of the fuel cell outlets and the fuel cell inlets such that a fluid flow may flow substantially parallel to the longitudinal axis of the apparatus in the first fluid conduits of the component and in the fuel cell unit and when passing from the component to the fuel cell unit or vice versa.

This application is a continuation of U.S. application Ser. No.14/527,024, filed Oct. 29, 2014, and claims benefit of European PatentApplication No. 13191429.3, filed Nov. 4, 2013, both of which areincorporated herein by reference. To the extent appropriate, a claim ofpriority is made to the above disclosed applications.

BACKGROUND

The application relates to an apparatus comprising a fuel cell unit anda component, such as for example a heat exchanger or a reformer. Theapplication also relates to a stack component for use for example insuch an apparatus or generally for use in combination with devicesrequiring a fluid flow passing through the device. The application alsorelates to a component unit comprising two stack components.

In order to optimize energy performance of fuel cell stacks, these arecombined with heat exchangers, afterburners, reformers or several ofthese components. Since space is often limited compact systems arepreferred. In WO-A-2004/082057 a modularly built fuel cell system isdescribed, wherein further components such as an afterburner, a heatexchanger and a reformer are subsequently arranged to a planar fuel cellstack. The outer geometry of the fuel cell stack and the furthercomponents match each other. Through bore holes in the plates and tubesarranged in the components, fluid is guided within the components andfrom one component to another. Plates are positioned perpendicular tothe general flow direction, so that the flow has to be guided by tubesfrom one component to another. Deflection plates may be required tobridge individual fluid channels in the system. Thus, this system bearshigh pressure drop and non-uniform temperatures due to fluid flowdeflection and requires additional space to accommodate the connectingelements between components.

Therefore, there is a need for a compact apparatus comprising a fuelcell unit and a component such as for example a heat exchanger, areformer, a preheater or an afterburner, which apparatus provides goodflow characteristic. There is also a need to provide a component unitcomprising two stack components to form for example such an apparatus ora stack component for use for example in such an apparatus, to supportthe overall performance of such a combined system.

SUMMARY

According to an aspect of the invention there is provided an apparatuscomprising a fuel cell unit with a plurality of fuel cells arranged inparallel defining a longitudinal axis of the apparatus and defining amain flow direction coaxial to the longitudinal axis of the apparatus.Therein fuel cell inlets and fuel cell outlets are arranged at oppositeends of the fuel cell unit and in line with the main flow direction. Theapparatus further comprises a component comprising first fluid conduitsarranged parallel to the main flow direction. The first fluid conduitscomprise first fluid inlets and first fluid outlets arranged at oppositeends of the component and in line with the main flow direction. Thecomponent is arranged adjacent the fuel cell unit such that at least oneof the first fluid inlets and the first fluid outlets of the componentare arranged adjacent at least one of the fuel cell outlets and the fuelcell inlets such that a fluid flow entering the apparatus may flowsubstantially parallel to the longitudinal axis of the apparatus in thefirst fluid conduits of the component and in the fuel cell unit and whenpassing from the component to the fuel cell unit or vice versa.

The fuel cell unit and the component, preferably a heat exchanger or areformer, are arranged such that a fluid may flow essentially linearlyand along the main flow direction through the component and through thefuel cell unit thus forming a main fluid flow through the apparatusaccording to the invention. The adjacent arrangement of fuel cell unitand component and of the fuel cell inlets and the first fluid outlets ofthe component or the fuel cell outlets and the first fluid inlets of thecomponent, respectively, allow for an unhindered or undeflected passingof the fluid from the component to the fuel cell unit or vice versa(depending on the arrangement of component and fuel cell unit upstreamor downstream of each other along the main flow direction). No reversingor change of direction, by for example 90 degrees, of a flow directionbetween or within parts of the apparatus takes place in the apparatusaccording to the invention. This may provide an overall low pressuredrop in the apparatus, uniform flow velocity and uniform temperaturedistribution, as well as a compact design due to fewer componentsneeded. In addition, flow uniformity may be realized in the apparatusand in individual parts of the apparatus. Interfaces or tube connectionsbetween parts of the apparatus or within a component become obsoletefacilitating the realization of a compact apparatus. Enhanced energyefficiency may also be achieved due to improved temperature distributionin the apparatus. A component or fuel cell unit may be realized asmodule and combined to the apparatus according to the invention, whichmay facilitate the manufacture, installation and maintenance of theapparatus according to the invention. For example, a replacement of acomponent or of the fuel cell unit is facilitated. Also, a component maybe adapted more easily to a specific fuel cell unit design.

If the component is a plate stack comprising a plurality of platesarranged in parallel above each other, then the plates of the componentare arranged parallel to the main flow direction. If the fuel cell unitis a planar fuel cell unit comprising a plurality of plates arranged inparallel and above each other, then all plates of the apparatus may bearranged parallel to the main flow direction and especially alsoparallel to each other. However, the plates of the component or of theplanar fuel cell unit may be rotated around a rotational axiscorresponding to the longitudinal axis of the apparatus or to the mainflow direction, respectively. Such a rotation of component, fuel cellunit, further component or of several parts of the apparatus againsteach other, may for example be in the range of between 0 degree and 180degree, preferably 90 degree. Also in these embodiments, the plates ofall parts of the apparatus are arranged parallel to the main flowdirection. However, the plates of for example neighbouring stacks may bearranged for example perpendicular to each other.

In some preferred embodiments, the fuel cell unit is a unit of hightemperature fuel cells such as for example solid oxide fuel cells(SOFCs). Especially, in high temperature fuel cells fluids at hightemperatures may be further used and only part of the fuel for the fuelcells is used up in the fuel cells itself. Therefore, further efficiencymay be gained by optimizing the flow characteristics, especially whencombining the fuel cells with a heat exchanger or with a reformer orpreferably with both.

A main fluid flow flowing in the main fluid direction may for example bea cathode flow of the fuel cell and of the reformer and a hot gas flowthrough a heat exchanger. Preferably, the main fluid flow is the fluidflow with the higher volumetric flow rate through the fuel cell unit andthrough the components of the apparatus. Thus, the main fluidcorresponds to the first fluid through the component, while a secondfluid generally has a flow rate with a lower volumetric flow rate thanthe flow rate of the first fluid. The second fluid may also be the fluidflow with a lower mass flow rate than the first or main flow. However, alower volumetric flow may also be achieved by a fluid flow with the samemass flow rate but with lower temperature than the fluid of the mainflow (or first flow, respectively). By optimizing, especiallyuniformizing, a fluid flow with the higher volumetric flow ratesignificant efficiency of the apparatus may be gained. For example, acathode flow of a reformer may be higher than an anode flow by about twoorders of magnitude.

Also the flow of a second fluid in the second fluid conduits of thestack component may be optimized. The second fluid also flows parallelto the plates of the stack component.

A component may be arranged upstream or downstream of a fuel cell unit.Accordingly, it is the first fluid outlets of the component, which arearranged adjacent the fuel cell inlets (when the component is arrangedupstream of the fuel cell unit) or it is the fuel cell outlets, whichare arranged adjacent the first fluid inlets of the component (when thecomponent is arranged downstream of the fuel cell unit).

If one or several further components are provided in the apparatusaccording to the invention, such as for example a heat exchanger, areformer, an afterburner or a preheater, preferably also in furthercomponents conduits for a fluid are arranged such as to allow a firstfluid to flow into the main flow direction. An apparatus may thus beextended by further components without losing its flow characteristic orits compactness.

Advantageously, the component, for example as used in the apparatusaccording to the invention, is a reformer or a heat exchanger, forexample also in the version of an afterburner or a preheater. In somepreferred embodiments of the apparatus according to the invention, thecomponent is arranged on a, preferably upstream, side of the fuel cellunit and at least one further component is arranged on an, preferablydownstream, opposite side of the fuel cell unit. For example, a heatexchanger may be arranged on an upstream side of the fuel cell unit suchthat a hot gas stream may flow parallel to the longitudinal axis of theapparatus and enter the fuel cells of the fuel cell unit as cathodeflow. Upon leaving the fuel cell unit this cathode flow still flowsalong the main flow direction parallel the longitudinal axis of theapparatus into and through the reformer arranged downstream and adjacentthe fuel cell unit.

In such an arrangement of the apparatus, a second fluid flow in the heatexchanger may for example be a mixture of an anode gas from the fuelcell unit and a hot gas. This mixture is then oxidized in the heatexchanger. The produced heat is used for (further) heating up thecathode gas, which is then led into the fuel cells of the fuel cellunit. Discharge outlets from the fuel cell unit may thus directly beconnected to second fluid inlets of the adjacently arranged heatexchanger. Heat produced in the fuel cell unit may be used for thereforming action in the reformer arranged further downstream. If theheat exchanger is arranged downstream of the fuel cell unit, the secondfluid may for example be a cool gas or cool liquid that is heated by thehot first fluid of the heat exchanger.

According to an aspect of the apparatus according to the invention, aheight and a width of the fuel cell unit corresponds to a height and awidth of the component. The geometrical matching of the parts of theapparatus according to the invention allows a very compact design of theapparatus and enhanced flow and temperature characteristic. An adjacentarrangement of the individual parts require no further adaptors and mayeasily be supplemented with further matching components. While the fuelcell unit may be a planar stack of fuel cells or also a stack of tubularfuel cells, the components, especially heat exchangers and reformerspreferably are plate stacks. In these plate stacks the width of theplates of a component corresponds to the width of the fuel cell unit.The heights of the stacks match each other in height, accordingly, thatis, component and fuel cell unit have a same height. A length of thestacks may be adapted to the required physical or chemical process to beperformed in the component or to specifications of the adjacent fuelcell unit or components. For example, a geometrical matching of the orof further components and the fuel cell unit include adjustment of thenumber of plates in a component stack, so that the height of the stackis the same as the height of the next component, for example a fuel cellstack. By this, the width and height of the outlet of for example a heatexchanger may be identical to the width and height of the fuel cellstack.

By a geometrical matching of the component and the fuel cell unit, amatching of the ‘core element’ or ‘core stack’ is meant, that is, thatportion of the component is referred to, where the physical or chemicalprocess of the component is performed. The component typically comprisessecond inlets and second outlets for a second fluid, such as for examplea cool or hot fluid for a heat exchanger or an anode fluid for thereformer. These supply inlets and discharge outlets do not form part ofthe core stack but may extend for example to two opposing sides of theapparatus. Also the fuel cell unit may be provided with supply inlets,for example with one tubular inlet or a set of small tubes, eachconnected to a segment of the fuel cell unit.

First fluid inlets and outlets as well as fuel cell inlets and outletsarranged in-line with the main flow direction, may be mechanicallyattached to each other. Preferably, inlets and outlets of adjacent partsof the apparatus are not mechanically attached to each other. Thecomponent and the fuel cell unit are arranged adjacent each otherpreferably such that it is excluded that the main fluid flow (or firstfluid) is mixed with another fluid, for example a second fluid of acomponent. The adjacent arrangement is also performed to support asubstantially linear flow along the main flow direction in the apparatusand such that the main flow direction is substantially parallel to thelongitudinal direction of the apparatus. The main flow beingsubstantially parallel to the longitudinal axis may also include smalldeviations from the parallel direction, for example due to differentinlet or outlet forms and sizes of adjacent parts of the apparatus.

In preferred embodiments of the apparatus according to the invention,the component comprises a plurality of plates arranged parallel to andabove each other forming a stack component. Through the special guidingof the main fluid flow according to the invention and preferably also offurther flows, described herein, an entire surface of the plates isusable for guiding a fluid flow along the plates. Spacers may bearranged along edges of plates and between individual plates to separatethe plates. By this, a single continuous conduit is created between theplates for a fluid to be guided between the plates. The spacers maydirectly serve for closing the sides between plates. A conduit may forexample also be formed by accordingly formed plates (profiled plates),for example through die forming or stamping. In these cases, the edgesmay directly be sealed by welding or brazing. Next to spacers or otherclosing means for closing sides of plates, no openings or tubes for aflow passage through the plates or perpendicular to the plates arepresent or required. Thus, the entire surface of a plate in thecomponent is available for guiding a fluid along the plate. By this, forexample, also the entire surface is available for a physical or chemicalprocess, for example a heat exchange or reforming process. In addition,side zones of plates may for example be used for optimizing a flowdirection while still a large central zone of the plates is availablefor a heat exchanging or other process the component is intended to beused for. Also no redirecting of a flow from one plate to aperpendicularly arranged inlet or outlet tube takes place in theapparatus according to the invention. Also no dividing elements arepresent within a first or second conduit, which would separate theconduits into individual small channels which might lead to significantpressure drop and non-uniform heat exchange. Thus, a flow, as well aspressure and temperature in the flow is more uniform.

According to an aspect of the apparatus according to the invention, agap is arranged between the fuel cell unit and the component. By thegap, no mechanical connection inside and between the fuel cell unit andthe component is required or available (except for an outer housing).This facilitates installation, manufacture and maintenance of theapparatus according to the invention. Also more flexibility in the kindof apparatus to be manufactured is available. For example, individualparts may be manufactured as modules and may be replaced individually.For example, also a fuel cell unit may be replaced by a different typeof fuel cell unit. By the provision of a gap, no further interfaces ordeflection plates are required. This not only reduces costs but alsoallows for an even more compact manufacture of the apparatus. Inaddition, uniformity of the main fluid flow is further supported andpressure loss due to the presence of mechanical elements may beprevented.

If several components are provided, preferably all components arearranged adjacent each other or adjacent the fuel cell unit,respectively, and a gap is provided between all the components andbetween the components and the fuel cell unit.

A gap may have a width for example in the range between 1 mm and 25 mm,for example between 2 mm and 15 mm, for example between 3 mm and 5 mm.

According to yet another aspect of the apparatus according to theinvention, the apparatus further comprises a main inlet with an inletdistribution portion, wherein a depth of the inlet distribution portionpreferably varies, preferably along the height of the component. Theinlet distribution portion is arranged adjacent the fuel cell unit oradjacent the component, depending on which part of the apparatus isarranged most upstream. A main fluid may be introduced through a maininlet opening into the main inlet. The main fluid is then distributedinside the inlet distribution portion over preferably an entire side ofthe apparatus, preferably over the entire height and width of the fuelcell unit or of the core stack of a component, respectively. By varyingthe depth of the inlet distribution portion of the main inlet, anextension of the inlet distribution portion in the longitudinaldirection of the apparatus is varied. Advantageously, an end region ofthe inlet distribution portion versus a main inlet opening, for exampleversus the top of the apparatus, is wider than an end region of theinlet distribution portion opposite the main inlet opening, for exampleversus the bottom of the apparatus. By this, the main fluid may enter anentire side of the fuel cell or component, respectively. By varying thedepth of the inlet distribution portion the main flow may be uniformlydistributed over an entire stack, despite the fact that a fluid inlet isarranged at a centralized location only. This further supports theperformance of the apparatus according to the invention.

The apparatus according to the invention may further be provided with amain outlet comprising an outlet collection portion. The outletcollection portion may be constructed similar to the main distributionportion, while for example a depth may be different than the depth ofthe inlet distribution portion. The main outlet is arranged adjacent themost downstream part of the apparatus, for example adjacent a furthercomponent. Preferably, a small gap of a few millimeters is providedbetween the main inlet and the part of the apparatus arranged adjacentthe main inlet, as well as between the main outlet and the part of theapparatus arranged adjacent the main outlet.

According to another aspect of the apparatus according to the invention,the component further comprises second conduits with a second fluidinlet and a second fluid outlet. The second conduits are adapted for asecond fluid to pass through the component. Since most components usedin the apparatus according to the invention require a second flow, suchas a heat exchanger (hot and cool flow) or a reformer (hot and fuelcontaining flow), an optimization of a second flow in the component,especially an optimization with respect to the first flow flowing in themain flow direction may further support the overall performance of theapparatus according to the invention. Overall performance may beachieved without exchanging mass flow between individual fluids.

Preferably, the second fluid inlet and second fluid outlet are arrangedalong the height of the component or of a stack, respectively, and arearranged at opposite sides of the stack. By this, a supply of secondfluid may be provided at one side of the component only (for example atop side), and is distributed over the entire height of the component inthe second inlet. Then the second fluid flow enters the second conduits,passes the second conduits, which preferably also extend over the entiresurface of the plates, and leaves the component by the second fluidoutlet. For further optimizing a flow in the component, the second fluidinlet may be arranged in an upstream region of a side of the componentand the second fluid outlet may be arranged at a downstream region of anopposite side of the component. By this, the second fluid may enter thecomponent from a side of the component but then be made to flowessentially parallel to the main flow direction in a central zone of thecomponent and leave the component at the opposite side. Such a co-flowarrangement in a central zone may be preferred in, for example, a heatexchanger or also a reformer. However, for a counter-flow arrangement,the second fluid inlet may also be arranged at a downstream region of aside of the component and the second fluid outlet may be arranged at anupstream region of the opposite side of the component.

In a compact arrangement, a width of the apparatus and of the componentaccordingly, may be larger than the length of the component, that is,than the extension of the component in the longitudinal direction of theapparatus. Thus, the second fluid flow has to be distributed over theentire width of the component, preferably evenly. This is preferablydone such that a central zone of the second conduits of the plates,respectively, preferably covers a large section of a cross section ofthe component and preferably such that a homogeneous flow with a lowvelocity is achieved within this central zone. By this, any process tobe performed in the component may be supported.

According to a further aspect of the apparatus according to theinvention, the component further comprises obstructions means in thesecond conduits. Advantageously, obstruction means are provided forcausing a locally variable pressure drop or locally varying fluidvelocity of the second fluid in the second conduits of the component. Bylocally varying the flow characteristic, a distributing, guiding,collecting, heat exchange, chemical reaction or a combination thereof ofthe second fluid flow in the second conduits may be supported andaltered. Fluid characteristic may also be adapted according to thegeometry of the component or to other requirements of the apparatusaccording to the invention by appropriate selection of obstructionmeans. For example, a distribution of the second fluid over the width ofthe component and a collection of the second flow to be directed to thesecond fluid outlet may be supported. Advantageously, differentobstruction means are arranged in inlet distribution zone, in centralzone and in outlet collection zone of the second conduits. Preferably,the different obstruction means are such that a pressure drop of thesecond fluid caused by the obstruction means in the central zone ishigher than the pressure drop caused in the inlet distribution zone andin the outlet collection zone. Such a different pressure drop may forexample also be achieved by providing obstructions in the central zonebut not in the inlet distribution zone and in the outlet collectionzone. In order to support a distribution in the inlet distribution zoneand a collection in the outlet collection zone, obstruction means mayalso vary inside a zone. For example, obstruction means may be providedsuch that close to an inlet or outlet only low pressure drop is caused,while close to a respective opposite side of the inlet or outlet and inthe central zone high pressure drop is caused. Preferably, obstructionmeans are adapted to a flow direction.

Preferably, obstruction means are structures provided in conduit wallssuch as structures in a plate surface forming the conduit wall.Structures may be profiles in plates with a periodic set of ridges andvalleys. Ridges and valleys may for example have a smaller period in thecentral zone of the plates, or have a different profile that representsa lower hydraulic diameter. This may also facilitate a heat exchange inthe central area of the component.

Structures may also for example be realized by a rough surface, forexample a coating of a conduit wall. A coating may also cover only partof the central zone or of another zone of the plate. A coating may forexample be a catalytic coating, for example in at least part of thecentral zone of a heat exchanger or a reformer. By this, catalyticreactions may be limited to a specific zone of the component. This zonemay be chosen so that the reactions only take place in an area where forexample the flow is uniform, where a temperature profile is best suitedfor the reactions to occur or for example for reaction heat to beexchanged with the other (main) flow in an efficient manner.

In addition, a thickness of a coating may reduce the remaining thicknessof the flow conduit, so that pressure drop increases in the coatedsection. This further facilitates the uniformity of the flow in thissection.

If obstruction means are realized in the form of a plate profile, theseare designed such as to preferably not influence a flow distribution inthe main flow path. However, since the main flow is large and alreadyhas a large pressure drop, it may be desirable to reduce the pressuredrop in the main flow conduit. This may for example be done by reducingthe open space between ridges of plates. The open space between theseridges and valleys will then be larger at the other side of the plates,that is, the side of the main flow. By this, the pressure drop in thepath of the main flow may be reduced, while the pressure drop of thesecond flow is increased.

According to a further aspect of the apparatus according to theinvention, a main inlet opening and a main outlet opening is arranged atopposite ends of the apparatus and such to enable a main fluid supplyand a main fluid discharge from a same side of the apparatus. By this, afluid supply to and a discharge from the apparatus is facilitated.Preferably, fluid is supplied and discharged from a top side of theapparatus. Preferably, all inlets and outlets of parts of the apparatusare arranged such that all fluid supplies and all fluid discharges maybe arranged on a same side, preferably a top side, of the apparatus. Bythis, an apparatus may for example be inserted into a compartment whichsize matches the size of the apparatus. For example, second fluid inletsand outlets may be arranged such, for example at the sides of theapparatus, so that they are adjacent to the supply inlets and dischargeoutlets of the fuel cell stacks, where they may be connected to.Installation and maintenance may then be performed from above theapparatus without need of access to lower parts of the apparatus.

It is advantageous to have no inlets and outlets at the bottom of theapparatus. By this, the apparatus may be mounted on a flat surface, forexample a flat insulation material or a steel plate, for example bearingthe weight of the complete apparatus.

According to another aspect of the invention, there is provided acomponent unit comprising a first stack component and comprising asecond stack component. The component may, for example, be combined witha fuel cell unit for forming an apparatus as described herein. Each ofthe first stack component and the second stack component comprise aplurality of plates arranged parallel to a main flow direction and at adistance to each other forming a stack. The stacks are open at a frontside and at a back side for a first fluid to enter the stack at thefront side, to pass through the stack along the main flow direction andto leave the stack at the back side. Each of the first and the secondstack further comprise second fluid conduits with a second fluid inletand a second fluid outlet. The second fluid inlet is arranged at alateral side of the stacks and the second fluid outlet is arranged at anopposite lateral side of the stacks. In the component unit, the firststack component and the second stack component are arranged at apredefined distance to each other. The open back side of the first stackcomponent is arranged parallel to the open front side of the secondstack component at the predefined distance. In preferred embodiments,the component unit further comprises a stabilizing frame. The frame isdesigned for stabilizing the first stack component and the second stackcomponent at the predefined distance and position relative to each otherduring handling and operation of the component, especially duringoperation at different temperatures. The stabilizing frame may preventthat the components shift, for example horizontally or vertically, orrotate relative to each other. Such a shift or rotation may for examplebe caused by thermal expansion or creep. A displacement against eachother can deflect or obstruct the flow as it passes through theapparatus substantially parallel to the longitudinal axis of thecomponent unit or apparatus, respectively. A stabilizing may support orguarantee the optimal working of the components, especially at differenttemperatures and pressures, for example during start-up, continuousoperation and cool down. These events can cause rapid or non-uniformheating of parts of the component and may cause deformations due to thethermal expansion or due to creep. Yet further, the frame may fix thesize of a cavity in between the two components, especially also atdifferent temperatures and pressures such as may be present duringstart-up, continuous operation and cool down. The stabilizing frame maythus provide the component unit for a defined application, for example acombination with a specific fuel cell unit.

According to yet another aspect of the invention there is provided astack component for example for use in a component unit or in anapparatus according to the invention and as described herein. The stackcomponent comprises a plurality of plates arranged parallel to a mainflow direction and at a distance to each other forming a stack. Thestack is open at a front side and at a back side for a first fluid toenter the stack at the front side, to pass through the stack along themain flow direction and to leave the stack at the back side. The stackcomponent further comprises second fluid conduits with a second fluidinlet and a second fluid outlet. The second fluid inlet is arranged at alateral side of the stack and the second fluid outlet is arranged at anopposite lateral side of the stack. At least one of the plates of theplurality of plates forming the second fluid conduits comprises acentral zone arranged next to an inlet distribution zone and next to anoutlet collection zone, wherein the central zone comprises obstructionmeans.

Preferably, second fluid inlet and second fluid outlet as well as theobstruction means in the central zone of the at least one plate arearranged such that a second fluid entering the stack component viasecond fluid inlet is caused to flow substantially in the main flowdirection in the central zone of the at least one plate.

Advantageously, at least one of two plates forming a second fluidconduit in between the two plates is provided with a central zonecomprising obstructions means.

According to an aspect of the stack component according to theinvention, at least two of the inlet distribution zone, outletcollection zone and central zone comprise different obstruction means.

According to another aspect of the stack component according to theinvention, at least one of the inlet distribution zone and the outletcollection zone comprises a variable extension along the main flowdirection. Preferably, the extension along the main flow direction ofthe inlet distribution zone or of the outlet collection zone or of bothvaries linearly along the front side. Preferably, the size of the inletdistribution zone diminishes with distance from the second fluid inlet.Preferably, the size of the outlet collection zone diminishes withdistance from the second fluid outlet. Preferably, inlet distributionzone or outlet collection zone or both are wedge-shaped.

Inlet distribution zone and outlet collection zone may be symmetric withrespect to form, size and obstruction means. An entire plate may bepoint symmetric with respect to the center of the plate.

Preferably, an inlet distribution zone extends substantially over theentire front side of the at least one plate, and the outlet collectionzone extends substantially over the entire back side of the at least oneplate. If the inlet distribution zone and the outlet collection zone iswedge-shaped, the central zone has the form substantially of aparallelepiped upon use of rectangular plates. If obstruction means,such as for example surface structures, are provided in the inletdistribution zone or the outlet collection zone or in both, such surfacestructures are preferably more expressed (more dense, higher etc.) inparts of the inlet distribution zone remote from the second fluid inletand in parts of the outlet collection zone remote from the second fluidoutlet than in parts next to inlet or outlet.

According to some preferred embodiments of the stack component accordingto the invention, the stack component further comprises at least one ofa main inlet portion arranged adjacent the front side of the stackcomponent or a main outlet portion arranged adjacent the back side ofthe stack component. The main inlet portion is provided for distributinga main fluid flow over an entire height of and into the stack component,while a main outlet portion is provided for collecting a main fluid fromthe entire height of the stack component and guiding the main fluid to amain outlet opening. The main outlet portion and the main inlet portionmay have a varying depth, preferably varying along the height of thecomponent. Preferably, the main inlet portion or the main outlet portionor both are wedge-shaped.

Preferably, a stack component is a heat exchanger, for example also inthe form of an afterburner, or preheater or reformer to be combined witha fuel cell unit or with a catalytic converter or similar. However, thestack component may also be designed such as to comprise not only anindividual component but also a fuel cell unit or a further component.

Thus, according to an aspect of the stack component according to theinvention, the plurality of plates further comprise sections withchemically active surfaces, preferably catalytically active surfaces,adapted for use in a fuel cell unit. A first part of the stackcomponent, for example an upstream part, comprises the second fluidconduits and is adapted to form a heat exchanger stack or a reformerstack. A second, for example downstream or further downstream, part ofthe stack component comprises the sections such that the second part ofthe stack component is adapted for use as a fuel cell unit.

In such a stack component, the plates have a length, which extends notonly over the length of for example a heat exchanger or of a reformerbut also extends further over the length of a fuel cell unit.Accordingly, parts of the plates comprise physical and chemicalproperties of the function to be performed by that part of the platestack. For example, if an upstream component shall be a heat exchangeror a reformer, the upstream first part of the plates compriseobstruction means for second fluid conduits and possibly portions with acatalytically active surface for a reforming or other chemical reaction.The plurality of plates arranged above each other comprising the secondfluid conduits then forms the heat exchanger or reformer (or heatexchanger or reformer part of the stack component). A further downstreamsecond part of the plates is coated by corresponding chemically activesubstances in order for that part of the plates to form bipolar platesfor use as electrodes in a fuel cell. That second part of the platestack component comprising the further downstream second parts of theplates then forms a planar fuel cell unit.

By such a construction of component and fuel cell unit, a geometricalmatching of height and width of a stack component or an apparatus isautomatically given. Also a main fluid flow direction is along theplurality of plates with no gap between a component and a fuel cellunit. Thus, further flow uniformity, temperature uniformity, a compactarrangement with fewer single components may be achieved.

If the parts of the apparatus according to the invention as describedabove are plate stacks, the individual plate stacks may be modules to bearranged next to each other to form an apparatus according to theinvention. However, the plates of the individual parts may be made ofone plurality of plates only, which plurality of plates extends over acomponent and over a fuel cell unit and possibly further components. Theindividual parts of the plates are prepared and adapted accordingly toperform their respective function of the parts of the apparatus.

Advantages and further aspects of the stack component according to theinvention and the component unit comprising two stack components havebeen described referring to the apparatus above and will therefore notbe repeated. In the stack component the front side corresponds to a longside of the apparatus and the extension along the front side correspondsto the width of the apparatus accordingly.

The stack component as well as the component unit is preferably used incombination with a high temperature fuel cell unit or incorporates ahigh temperature fuel cell to form an apparatus for example as disclosedherein. However, with the stack component according to the invention,further devices requiring at least one fluid flow may by optimized. By acombination of such a device with a stack component according to theinvention and as described herein relating to a fuel cell unit, a mainflow direction is defined and flow uniformity of the main fluid flow aswell as of second fluid flows may be achieved. Such a further device mayfor example be a converter, such as a catalytic converter as used forexample in exhaust systems of motor vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described with regard to embodiments, which areillustrated by means of the following drawings, wherein:

FIG. 1 shows a schematic view of an apparatus according to theinvention;

FIG. 2 is a cross section through the apparatus of FIG. 1;

FIG. 3 is a perspective view of a reformer for use in an apparatusaccording to FIG. 1;

FIG. 4 is a schematic through-view of the apparatus of FIG. 1 withsecond fluid flow indicated for an intermediate heat exchanger andreformer section;

FIG. 5 is a flow simulation for a second fluid flow in a reformer or aheat exchanger;

FIG. 6 shows a component unit with two assembled stack components.

DETAILED DESCRIPTION

FIG. 1 shows a compact rectangular apparatus with a fuel cell stack 2,for example a solid oxide fuel cell (SOFC) stack combined with areformer 3 and heat exchanger 1. The heat exchanger 1 is arranged on anupstream side of the fuel cell stack 2 and the reformer 3 is arranged onthe opposite downstream side of the fuel cell stack 2. Reformer 3 andheat exchanger 1 are a multiple plate reformer and a multiple plate heatexchanger, wherein the individual plates are arranged parallel and at adistance to each other in a bottom top arrangement in the embodiment asshown. The fuel cell stack 2 may be a parallel arrangement of individualplate fuel cells or tubular fuel cells, with the tube axis or platesarranged parallel to the length 500 or longitudinal axis of theapparatus. The outer dimensions of the heat exchanger 1, fuel cell stack2 and reformer 2 correspond to each other, especially a stack height 300of all three parts 1,2,3 is identical and a plate width 400 of heatexchanger 1 and reformer 3 is identical and corresponds to the stackwidth 400 of the fuel cells. The longitudinal ends of the apparatus areprovided with a main inlet 5 and a main outlet 6. By these, a main fluidis directed into the apparatus and guided along a main fluid direction100, through the heat exchanger 1, the fuel cell 2 and subsequentlythrough the reformer 3, before the main fluid is guided out of theapparatus through main outlet 6. The main flow direction 100 through theparts 1,2,3 of the apparatus is also indicated in FIG. 2, which is aview onto a longitudinal cross section of the apparatus shown in FIG. 1.

The main inlet 5 is provided with an inlet opening 51 and a wedge-shapedinlet distribution portion 50. The wedge-shaped inlet distributionportion 50 is arranged adjacent the heat exchanger plate stack 1. Inletopening 51 and outlet opening 61 are arranged at the top of theapparatus. Inlet distribution portion 50 is broadest at the top of thestack and smallest at the bottom of the stack (with reference to thelongitudinal direction of the apparatus). The main outlet 6 is providedwith an outlet opening 61 and a wedge-shaped outlet collection portion60. The wedge-shaped outlet collection portion 60 is arranged adjacentthe reformer stack 3 and is also broadest at the top of the stack andsmallest at the bottom of the stack. The sizes of the wedge-shapeddistribution portion 50 and collection portion 60 may be adapted tooptimize a flow velocity, pressure drop, flow uniformity and flowdistribution or collection, respectively, in the respective portions 50,60. For example, in the embodiment shown, the size of the wedge of thecollection portion 60 is larger in depth that the size of the wedge ofthe distribution portion 50.

The parts of the apparatus, heat exchanger 1, fuel cell 2 and reformer 3are directly arranged adjacent each other, separated only by a small gap55, 65. The gaps 55,65 are typically in the range of a few millimetres,for example between 2 and 10 mm. The gap size may be adapted to the sizeof the apparatus. No interfaces, tubes, adaptors, manifolds oradditional pressure drop plates are provided between the individualparts of the apparatus. Also main inlet 5 and main outlet 6 are arrangedadjacent the heat exchanger 1 and reformer 3, separated only by smallgaps 45,75. The main fluid may be distributed to all the first conduitsby the main inlet 5 without any openings or connecting conduits requiredin the plates of the stack. In addition, the main fluid may be collectedfrom all the first conduits by the main outlet 6 without any openings orconnecting conduits in the plates of the stack.

The main or first fluid flow of the heat exchanger 1 and of the reformer3 is “inline” with the main fluid flow through the fuel cell stack 2 andthis main flow is flowing in the main flow direction 100. The plates ofthe heat exchanger 1 and reformer 3 are arranged parallel to the mainflow direction 100 to enable such a direct and undeflected flow. Thefuel cells are arranged such that the main flow, typically a cathodeflow, is arranged in a longitudinal direction of the fuel cell stack andof the apparatus. One, preferably, major flow of the heat exchanger 1,for example a hot gas flow, led into the apparatus through main inlet 5flows from the wedge-shaped inlet distribution portion 50 along theentire height 300 into the heat exchanger 1 and through the heatexchanger in the longitudinal direction of the apparatus. Also the mainflow through the reformer 3, preferably a cathode flow as well, flows inthe same longitudinal direction through the entire reformer until theflow enters the wedge-shaped main outlet portion 60.

By a straight main fluid flow through the apparatus, low pressure drop,uniform temperature and pressure distribution in the apparatus may beachieved. In addition, a compact apparatus requiring less components atreduced costs may be realized.

To further optimize the performance of the fuel cell 2, and of theentire apparatus, also the second flows in the heat exchanger 1 andreformer 2 are optimized for example as shown in FIG. 1 and FIG. 2. Thesecond, volumetrically smaller flows, indicated by arrows 150, areintroduced from the side into the heat exchanger 1 and reformer 3,respectively, via second inlet channels 110,310. The second fluids areguided out of the heat exchanger 1 and reformer 3, respectively, viasecond outlet channels 120,320, also sideways but on an opposite lateralside of the components. By this, second fluids may be provided to anddischarged from the apparatus from the side of the stacks 1,3 andthrough respective second fluid inlet and outlet openings111,311,121,321 arranged at the top of the stack. Also secondary supplyinlets and outlets 21 for the fuel cells are arranged at the top side ofthe apparatus.

This facilitates an installation of the apparatus according to theinvention since supply or discharge lines may be provided at and fromthe top of the apparatus. Especially, no inlets or outlets are arrangedat the bottom of the apparatus.

The second fluid may be distributed to all the second conduits by thesecond inlet channels 110,310 without any openings or connectingconduits required in the plates of the stack. In addition, the secondfluid may be collected from all the second conduits by the second outletchannels 120,320 without any openings or connecting conduits in theplates of the stack.

The respective second fluids are introduced into the componentsperpendicular to the main flow direction 100, are redirected such as toflow parallel to the main flow in a central zone 13,33 of the components1, 3 and are redirected again to leave the components 1,3 perpendicularto the main flow direction 100.

The plates of the components of the apparatus comprise different zones,such as inlet distribution zones 11, 31, central zones 13,33 and outletcollection zones 12, 32 of heat exchanger 1 and reformer 3. Inlet andoutlet zones directly follow the second fluid inlets 110,310 and secondfluid outlets 120,320, respectively. The inlet and outlet zones 11,31extend over the entire width 400 or substantially the entire width ofthe apparatus and have the shape of a triangle or the form of a wedgewhen seen an a three dimensional manner (intermediate conduits for themain fluid flows are omitted in FIG. 1). The central zones 13,33 havesubstantially the forms of a parallelepiped. Inlet, central and outletzone generally differ by their influence on second flow behavior.Typically, structures influencing such a flow behavior are arranged inone, two or all three zones. Depending on the required pressure drop,flow direction or flow uniformity that shall be achieved in therespective zone, structures are provided and arranged accordingly.Preferably, structures causing high pressure drop are arranged in thecentral zones 13,33. Inlet zones 11,31 and outlet zones 12,32 may beprovided with no or less structure than the central zones. Structuresmay especially be different in a zone itself.

FIG. 3 shows a reformer 3 representing a stack component of the presentinvention with rectangular plates 301 arranged parallel to each other ina top to bottom arrangement forming a plate stack 30. The two lateralsides of the plate stack 30 are provided with side wall portions 311closing part of the sides of the stack 30 to the environment. The sideparts of the reformer not closed by the side wall portions 311 are openand form second fluid inlets and second fluid outlets 3200 accordingly.The second fluid may for example be a fuel containing anode flow.

The open front side allows the entry of a fluid flow between the plates301 along the entire height of the reformer stack 30. The fluid flowpasses through the reformer between the plates in the main flowdirection 100 and leaves the reformer at the back side again along theentire height of the reformer. From there the main flow may either flowstraight into a fuel cell stack or into a further component or into amain inlet collection portion as described with reference to FIG. 1.

In FIG. 4 a through-view of an apparatus according to FIG. 1 isschematically shown. The zones of the plates are shown for anintermediate second conduit of a heat exchanger and reformer platearrangement.

A second fluid at high velocity enters the heat exchanger 1 via secondfluid inlet channel 110 through second fluid inlet into the secondconduit. The second fluid is slowed down gradually in the wedge-shapedinlet distribution zone 11 of the heat exchanger 1. The fluid flow isredirected from the direction perpendicular to the longitudinal axis ofthe apparatus to flow essentially parallel to the longitudinal axis ofthe apparatus in the central zone 101 of the second conduit of the heatexchanger (corresponding to the main flow direction 100). It is mainlyin the central zone 101, where the heat exchanging process takes place.In this central zone 101 the flow velocity is slow and substantiallyhomogeneous over about the entire central zone 101. When the secondfluid reaches the opposite end of the second conduit between two plates,the flow is redirected again to flow perpendicular to the main flowdirection 100 and is led along the outlet collection zone 12 to secondfluid outlet channel 120. In the outlet collection zone 12 the secondfluid gains velocity such that the second fluid flow leaves the heatexchanger at a higher velocity again. Different flow velocities anddifferent pressure drop zones in the heat exchanger may for example beachieved by appropriate surface structuring of the plates of the heatexchanger. This will be explained in more detail with reference to thereformer in FIG. 5. The structure of the second conduit for the secondfluid flow of the reformer as well as of the guiding of the fluid flowin the reformer is basically the same as the one of the heat exchanger.

The second fluid in the heat exchanger may for example be a cool fluidsuch as a cool gas or a cool liquid, which is warmed up in the heatexchanger. The second fluid may for example also be a hot fluid with lowmass flow or a combination of two fluids such as a mixture of hot fluidand an anode gas, which may be oxidized in the second conduit. For thelatter application, the heat exchanger is preferably provided with acatalytically active coating to support the oxidizing reaction.

In FIG. 5 a fluid flow in a reformer is shown in an abstracted form bymeans of flow lines 151. The density of the flow lines indicates flowvelocity. The general second flow direction is indicated by arrows 150,wherein the main flow direction is again indicated by arrow 100.

The principle arrangement and design of the reformer zones 31,32,33 aresimilar to the ones of the heat exchanger in order to create a centralzone 33 with a uniform flow distribution and flow direction which isessentially parallel to the main flow direction 100. Therefore, in thecentral zone 33 a high pressure drop for a uniform flow and a low flowvelocity is provided. The latter supporting an efficient reformingaction and especially also in the case of the heat exchanger anefficient heat exchanging process. In the wedge-shaped internaldistribution and collection zones 31 and 32 preferably a pressure dropis low and may vary over the width of the plate 301. The inletdistribution zone 31 and the outlet collection zone 32 do not extendalong the entire width of the plate 301. The zones 31,32 end at adistance 315 before the end of the width of plate 301. Distance 315 ischosen and may be varied depending on the application of the component.Basically, by enlarging the distance 315 a fluid flow may be slowed downbefore reaching the bottom right corner and the top left corner of theplate 310 with respect to the embodiment drawn in FIG. 5. Thus, anaccumulation of fluid in these corners may be prevented and a homogenousdistribution of the flow over the central zone 33 may further besupported. Also the width 316 of the distribution and collection zones31,32 may vary and be larger or smaller depending on the application ofthe component.

The width is larger than the extension of the plate 301 in longitudinaldirection (main flow direction 100). By this, a rather large centralzone 33 with optimized flow characteristic is created.

Pressure drop may be influenced by surface structures or profiles of theplates of the reformer stack or of the heat exchanger stack,accordingly. Therefore, preferably a central zone 33 is provided withsurface structures, while distribution and collection zones 31,32comprise no or only little surface structures. Surface structures mayfor example be combined with a catalytic coating applied in the centralzone 33.

In FIG. 6 a component unit 9 is shown, wherein same reference numeralsare used for the same or similar elements. A first component, forexample a heat exchanger stack 1 is arranged opposite to and distancedat a distance 83 from a second component, for example a reformer stack3. A stack wall 113,313 at (or by) each of the components is formed bythe sum of plate side walls or the first fluid outlets of the heatexchanger 1, respectively as well as by the sum of plate side walls orthe first fluid inlets of the reformer 3, respectively. These two walls113,313 are arranged parallel to each other allowing a main flow 100 ofa first fluid to flow in a linear direction between the plates of andfrom the heat exchanger to and between the plates of the reformer. Noconnection means are present and a device, such as for example a fuelcell unit, may be inserted into the space provided between the twocomponents 1,3 making use of this compact and efficient arrangement oftwo components.

The so arranged stack components 1,3 are combined via a stabilizingframe 8 to form the component unit 9. Via the stabilizing frame 8 theposition between the two components may be fixed and the unit 9stabilized. This stabilization may be required to guarantee that thecomponents 1,3 maintain the right distance, and the same height andlateral position during operation also at different temperatures. Theframe prevents that one of the components shifts or rotates relative tothe other component, for example caused by thermal expansion or creep,as this can deflect or obstruct the flow as it passes through theapparatus substantially parallel to the longitudinal axis of theapparatus in the main flow direction 100. The stabilizing frame 8 mayhave a frame compartment for each of the components. A frame compartment80 may be provided for the heat exchanger 1 and another framecompartment 81 may be provided for the reformer 3, further stabilizingthese components against deformations by creep or differential thermalexpansion during operation. The middle compartment 82 is a space orcavity provided for a device the components shall be combined with toform for example an apparatus as described herein.

The invention has been described with reference to the embodiments shownin the drawings. However, it is obvious to a person skilled in the artthat many variations, modifications or changes are possible withoutdeparting from the scope of the invention. By way of example only, thearrangement of inlets and outlets or forms of main inlet and main outletmay vary. For example, the second inlets and second outlets may bearranged differently, also for example at different sides of thearrangement. Also, the manner how the conduits and obstruction means inthe conduits or the main inlet and main outlet, as well as the seconddistribution inlets and second collection outlets are embodied may bedifferent from these elements actually shown in the drawings. All suchvariations, modifications or changes are intended to be within the scopeof the invention which is defined by the appended claims.

1. Apparatus comprising a fuel cell unit with a plurality of fuel cellsarranged in parallel defining a longitudinal axis of the apparatus anddefining a main flow direction coaxial to the longitudinal axis of theapparatus, wherein fuel cell inlets and fuel cell outlets are arrangedat opposite ends of the fuel cell unit and in line with the main flowdirection; and further comprising: a component comprising first fluidconduits arranged parallel to the main flow direction, and the firstfluid conduits comprising first fluid inlets and first fluid outletsarranged at opposite ends of the component and in line with the mainflow direction, and wherein the component is arranged adjacent the fuelcell unit such that at least one of the first fluid inlets and the firstfluid outlets of the component are arranged adjacent at least one of thefuel cell outlets and the fuel cell inlets such that a fluid flowentering the apparatus may flow substantially parallel to thelongitudinal axis of the apparatus in the first fluid conduits of thecomponent and in the fuel cell unit and when passing from the componentto the fuel cell unit or vice versa.
 2. The apparatus according to claim1, wherein a height and a width of the fuel cell unit corresponds to aheight and a width of the component.
 3. The apparatus according to claim1, wherein a gap is arranged between the fuel cell unit and thecomponent.
 4. The apparatus according to claim 1, wherein the componentis a heat exchanger or a reformer.
 5. The apparatus according to claim1, wherein the component is arranged on one side of the fuel cell unitand at least one further component is arranged on an opposite side ofthe fuel cell unit.
 6. The apparatus according to claim 1, furthercomprising a main inlet with an inlet distribution portion, wherein adepth of the inlet distribution portion varies.
 7. The apparatusaccording to claim 1, the component further comprising second conduitswith a second fluid inlet and a second fluid outlet, the second conduitsfor a second fluid to pass through the component.
 8. The apparatusaccording to claim 7, wherein the second fluid inlet is arranged in anupstream region of a side of the component and the second fluid outletis arranged at a downstream region of an opposite side of the componentsuch that the second fluid may flow essentially parallel to the mainflow direction in a central zone of the second conduits.
 9. Theapparatus according to claim 7, the component further comprisingobstructions means in the second conduits.
 10. The apparatus accordingto claim 9, wherein different obstruction means are arranged in inletdistribution zone, in central zone and in outlet collection zone of thesecond conduits, such that a pressure drop of the second fluid caused byobstruction means in the central zone is higher than the pressure dropcaused by obstruction means in the inlet distribution zone and in theoutlet collection zone.
 11. The apparatus according to claim 1, whereina main inlet opening and a main outlet opening is arranged at oppositeends of the apparatus and such to enable a main fluid supply and a mainfluid discharge from a same side of the apparatus.
 12. A component unitfor use in an apparatus according to claim 1, the component unitcomprising a first stack component and comprising a second stackcomponent, wherein each of the first stack component and the secondstack component comprise a plurality of plates arranged parallel to amain flow direction and at a distance to each other forming a stack,wherein the stacks are open at a front side and at a back side for afirst fluid to enter the stack at the front side, to pass through thestack along the main flow direction and to leave the stack at the backside; each of the first and the second stack further comprising: secondfluid conduits with a second fluid inlet and a second fluid outlet, thesecond fluid inlet is arranged at a lateral side of the stacks and thesecond fluid outlet is arranged at an opposite lateral side of thestacks, wherein the first stack component and the second stack componentare arranged at a predefined distance to each other, and wherein theopen back side of the first stack component is arranged parallel to theopen front side of the second stack component.
 13. The component unitaccording to claim 12, further comprising a stabilizing frame formaintaining the first stack component and the second stack component atthe predefined distance and position relative to each other.
 14. A stackcomponent for use in an apparatus according to claim 1, comprising: aplurality of plates arranged parallel to a main flow direction and at adistance to each other forming a stack, wherein the stack is open at afront side and at a back side for a first fluid to enter the stack atthe front side, to pass through the stack along the main flow directionand to leave the stack at the back side; further comprising: secondfluid conduits with a second fluid inlet and a second fluid outlet, thesecond fluid inlet is arranged at a lateral side of the stack and thesecond fluid outlet is arranged at an opposite lateral side of thestack; wherein at least one of the plates of the plurality of platesforming the second fluid conduits comprises a central zone arranged nextto an inlet distribution zone and next to an outlet collection zone,wherein the central zone comprises obstruction means.
 15. The stackcomponent according to claim 14, wherein at least two of the inletdistribution zone, outlet collection zone and central zone comprisedifferent obstruction means.
 16. The stack component according to claim14, wherein at least one of the inlet distribution zone and the outletcollection zone comprises a variable extension along the main flowdirection.
 17. The stack component according to claim 14, the pluralityof plates further comprising sections with chemically active surfacesadapted for use in a fuel cell, wherein a first part of the stackcomponent comprises the second fluid conduits and is adapted to form aheat exchanger stack or a reformer stack, and wherein a second part ofthe stack component comprises the sections such that the second part ofthe stack component is adapted for use as a fuel cell unit.
 18. A stackcomponent for use in an apparatus according to claim 12, comprising: aplurality of plates arranged parallel to a main flow direction and at adistance to each other forming a stack, wherein the stack is open at afront side and at a back side for a first fluid to enter the stack atthe front side, to pass through the stack along the main flow directionand to leave the stack at the back side; further comprising: secondfluid conduits with a second fluid inlet and a second fluid outlet, thesecond fluid inlet is arranged at a lateral side of the stack and thesecond fluid outlet is arranged at an opposite lateral side of thestack; wherein at least one of the plates of the plurality of platesforming the second fluid conduits comprises a central zone arranged nextto an inlet distribution zone and next to an outlet collection zone,wherein the central zone comprises obstruction means.
 19. The stackcomponent according to claim 18, wherein at least two of the inletdistribution zone, outlet collection zone and central zone comprisedifferent obstruction means.
 20. The stack component according to claim18, wherein at least one of the inlet distribution zone and the outletcollection zone comprises a variable extension along the main flowdirection.